This is just another thought-terminating cliche not unlike "if it is free, you are a product" and I can't help but respond.
Large technological companies create ecosystems where smaller players can coexist with "hosts" in a mutually beneficial relationship. Ecosystem companies are not able to predict the future of the ecosystem, its evolution for all intents and purposes is mostly unpredictable. Sometimes the relationship works out, sometimes it doesn't.
Startups have 70-90% failure* rate, the possibility of the host cutting of some parts of the ecosystem to integrate their food chains into the corporate borg is factored in the business and investments strategies of the smaller companies.
You should not trust another company for your business model, but building your tech business in the ecosystem of a large fish is an absolutely valid and quite possibly lucrative strategy.
*definitions vary
EDIT success/failure